Hybrid vehicles are driven by multiple powerplants including, but not limited to an internal combustion engine and an electric machine. The electric machine functions as a motor/generator. In a generator mode, the electric machine is driven by the engine to generate electrical energy used to power electrical loads or charge batteries. In a motor mode, the electric machine supplements the engine, providing drive torque to drive the vehicle drivetrain.
During hybrid vehicle operation, the hybrid vehicle travels on various degrees of road grade, which is the road angle relative to horizontal. The degree of the road grade often influences driving behavior and vehicle operating parameters. Furthermore, it is desirable to be able to regulate certain vehicle operating conditions based on the road grade.